Temporal summation and critical duration in bee photoreceptors: a comparison of measurement methods

Temporal summation of visual stimuli by single retinular cells in the compound eye of the bee Melipona quadrifasciata were measured by three different methods. Critical duration was best defined by interpolating intensity-duration response functions. Measurement of responses to two types of equal-energy stimuli gave more precise evaluation of the degree of summation below the critical duration; single pulses produced an unexpected deviation from Bloch's Law.